public class Pillar {
	Geometry bottom;	//bottom是用抽象类Geometry声明的对象
	double height;
	Pillar (Geometry bottom,double height) {
		this.bottom = bottom;
		this.height = height;
	}
	public double getVolume() {
		if (bottom==null) {
			System.out.println("没有底，无法计算体积");
			return -1;							}										return bottom.getArea()*height;							}
}
